Integrated circuits generally include conductive, semiconductive, and insulative materials. Although various metals are used in the metallization of large-scale integrated circuits, many of such metals are difficult to fabricate in fine patterns because of the lack of adequate or suitable etching methods.
For example, copper is a well-recognized conductor. However, few integrated circuits having fine line patterns integrate copper as the conductor for metallization purposes because it is difficult to fabricate fine patterns of copper. There is a strong incentive to incorporate copper as a conductive material in integrated circuits because of its low resistivity, higher melting temperature relative to other metals, and higher electromigration resistance compared with other currently used conductive materials, such as aluminum alloys. As such, incorporation of copper as a conductive material in integrated circuits is desired so as to allow an increase in speed thereof.
One method of using copper for interconnect structures is by patterning the copper using a damascene-type method. Such a method employs the deposition of copper into predefined damascene trenches. Such a process, particularly when adjacent silicon-containing regions, requires that a diffusion barrier/liner layer be used within the trench. However, if the barrier thickness cannot be reduced as trench sizes become smaller, the impact on resistance of the conductor deposited in the trench is significant.
Further, the existing processing methods for patterning certain conductive materials, such as aluminum, are often ineffective for other conductive materials, such as copper. For example, dry etching methods are generally inadequate for providing thin copper conductor patterns.